Mind's eye can learn to see, study finds

WASHINGTON - People blind from birth can be taught to "see" images that are conveyed as sounds, says a new study that calls into question a longstanding belief about the limits of the human brain.

Devices that scan visual images and reinterpret regularities as sounds were used to retrain the brains of congenitally blind people in a study published in the journal Neuron. The authors at Hebrew University in Israel put people who had been blind since birth through 70 hours of training with a visual-to-auditory sensory substitution device.

Initially, the subjects were able to distinguish among faces, houses, everyday objects, body shapes and textures. Eventually, they were able to read letters and words, identify facial expressions and locate people's positions. In one video, a blind person is shown a picture of a woman with a ponytail and identified the hairstyle.

Blind people have long used the capability to use another sensory perception to compensate for blindness: Braille and blind walking canes allow people without sight to read and navigate. But when the authors of the current study put subjects in a brain scanner, they gained insight into the process by which training with a sensory substitution device allowed the mind's eye to "see."

The human brain is a remarkably efficient and adaptable organ: When an appendage such as a hand is amputated, or a sensory perception such as sight is lost, the specialized regions of the brain in which input from the hand or the eyes is processed are reassigned to other duties.

But scientists have long believed that the brain's adaptability is limited by early conditions. Not so, the current study finds.